IIP2 calibration is a stringent requirement for a cellular frequency division duplex (FDD) system due to finite isolation between a transmitter and a receiver. Due to a strong dependency between an in-phase path (I-path) and a quadrature-phase path (Q-path) during IIP2 calibration, an exhaustive search to find an optimal digital-to-analog converter (DAC) code that minimizes the I-path and Q-path second order intermodulation (IM2) tone amplitude simultaneously is frequently performed. An exhaustive search may be time consuming. Alternatively, an iterative search may be performed. However, an iterative search method suffers from a convergence issue within a few iterations due to IQ path dependency.
An initial optimal mixer DAC code may be preset during factory calibration. Due to process and/or temperature variation, an actual real-time optimal mixer DAC code may deviate from the initial preset mixer DAC code.